Table and suspended chair unit with centering apparatus

ABSTRACT

A support system for chairs suspended beneath a table top wherein plastic bearings are used to provide horizontal and vertical pivot surfaces and supports for chair suspension arms, a yieldable means is provided to limit rotation of each chair arm, and resilient means are provided for moving the chairs to a normally centered position.

[ 51 Apr. 25, 1972 United States Patent Black et al.

Allen 10/1970 Protzman...............................

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1541 TABLE AND SUSPENDED CHAIR UNIT WITH CENTERING APPARATUS [72] inventors: Herman both of Camarillo, Calif. [731 Assignees: Herman Richard R. Wright, ldaho Falls, Idaho part interest to each July 22, 1970 Primary Examiner-James T. McCall Attorney-B. Deon Criddle (22] Filed:

[57] ABSTRACT A support system for chairs suspended beneath a table top [21] Appl. No.:

1297/ 248/ 248/418 wherein plastic bearings are used to provide horizontal and 'A47c 39/00 vertical pivot surfaces and supports for chair suspension arms, .248/417, 418, 415; 297/142,

a yieldable means is provided to limit rotation of each chair 297/143 141 108/150 arm, and resilient means are provided for moving the chairs to a normally centered position.

16 Claims, 12 Drawing Figures [5 6 References Cited UNITED STATES PATENTS 7/1966 Black et a1.

P ATENTEDAPR 2 5 m2 unwml m VEN TORS HERMAN w. BLACK 8b N K. FULLMER KEITH w. NAYLOR 4 ATTORNEY PATENTEDAPRZS I972 1 3, 658 379 v l" lli mm INVENTORS:

HERMAN W. BLACK RICHARD R. WRIGHT DON K. FULLMER KEITH W. NAYLOR ATTORNEY PATENTEDAPR 25 m2 SHEET 3 BF 3 I i I I g 5 INVENTORS-' HERMAN W. BLACK RICHARD R. W HT DON K. FULLM KEITH W. NAYLOR ATTORNEY BRIEF DESCRIPTION OF THE INVENTION 7 l. Field of the Invention This invention relates to table and chair combinations of the type wherein at least one chair is suspended from beneath a table top. In the past, there have been many such support means proposed, but either they are too costly or bulky to be entirely satisfactory or they do not hold up under the strain of the heavy weights imposed on them through cantilevered support arms and the rotations occurring as the arms are turned beneath the table top. Also, when structural failure occurs, they may drop a person sitting on the end of a suspension arm to the ground, causing serious injury.

2. Prior Art There is shown in US. Pat. No. 3,262,733, for example, a table with suspended chair wherein a bearing washer is used to reduce friction and a channel and clamp arrangement maintain the vertical alignment of the rotating arms. Another support means is shown in US. Pat. No. 3,226,154, and in this patent abutting friction bearings which may be of bronze, for example, are provided to cooperate in a horizontal friction plane as the support arm for a seat is rotated.

While the above arrangements, and many others have been satisfactory for some purposes and to some extent, there has been a continuing need for a method of providing a more friction free support and especially one that can be built more economically than those heretofore known.

In addition, while previously known supports have incorporated stop means to positively limit swinging movement of the support arms so that seats supported thereon cannot engage the table edge, it has been found that the large torque imposed by a person sitting on a seat at the end of such a rotatable support arm may result in damage to the stop means and/or the pivot mechanism.

It has also been known to provide biasing means to swing a supported arm such that a seat carried thereby is moved beneath a table top, but, so far as we are aware there has not been a biasing means that will bias the arm in either direction of rotation to a central starting position wherein the seat is beneath the table top butthe seat back is held away from the table edge.

SUMMARY OF THE INVENTION Objects of the present invention are to provide a more friction free rotating support arm for a seat suspended beneath a table top; one that is economical to construct; one that is durable; and one that will insure free rotation of the arm for an extended time.

Other objects are to provide an easily installed mechanism for biasing the rotating arm so that it will swing the seat sup-. ported thereon beneath the table and yieldable means to limit such swinging motion but resilient enough to allow continued swinging beyond the normal stop position, thereby preventing damage to the arm support structure when a large moment arm force is applied to force such swinging.

Still further objects are to provide means to bias the rotating arm such that it is biased to a central starting position, whereby the seat thereon is out of the way beneath the table top and the arms automatically return the seats to a position where they are aligned and esthetically pleasing.

Principal features of the invention include a pin serving as a part of the yieldable means and as an emergency hanger rod for one of the arms; plastic bearings through which the arms are journaled and providing both horizontal and vertical bearing surfaces; and springs on the arms and cooperating pins on a cover plate to normally bias the arms to a position whereby the seats thereon are at a centered or starting position beneath the table or spring biased cam means to bias the arms to their centered or starting position.

Additional objects and features of the invention will become apparent from the following description taken together with the accompanying drawing which shows, for purpose of illustration only, a presently preferred embodiment of the invention.

THE DRAWINGS shown in FIG. 4;

FIG. 6, a front elevation view of the centering cam;

FIG. 7, a vertical section, taken on the line 7-7 of FIG. 6;

FIG. 8, a view like FIG. 4 of still another embodiment of the invention;

FIG. 9, a horizontal section taken on the line 9-9 of FIG. 8;

FIG. 10, a perspective view of a cam follower of the embodiment of FIG. 8;

FIG. 11, a similar view of the cam member; and

FIG. 12, a perspective view of a support bracket.

DETAILED DESCRIPTION Referring now to the drawings:

In the illustrated preferred embodiment the invention includes a table top 10 having a support means 11 therefor, a seat 12 and suspension means shown generally at 13 for suspending the seat beneath the table.

As illustrated, the table top 10 and support means 11 therefor, are essentially like those shown in US. Pat. No. 3,262,733, issued July 16, 1966 to Herman Wendell Black and Kae Durham Black and the suspension means 13 is suspended from one end of a horizontally extending arm 14, the other end of which is fixed to an upstanding post 15. However, it should be apparent that the suspension means 13 could as well be hung from other support and/or frame structure beneath the table top.

The suspension means comprises a channel member 16 having its flanges 16a and 16b turned inwardly beneath the table top and with the top end of the channel member fixed to the horizontally extending arm 14.

A rolled steel pin 17 is press-fitted through holes provided therefore in the upper ends of the flanges 16a and 16b to provide an emergency hanger rod and resilient limit means for one or more suspension arms 18.

Each suspension arm 18 has-a tubular cap 19 on the upper end of a vertically extending portion thereof. The cap is secured to the arm by a rolled steel pin 20, press-fitted through aligned holes provided therefor in the wall of the cap and the arm.

Arcuate slots 21 and 21a are provided in the sidewall of cap 19, above the upper end of arm 18 and when the pin 17 is inserted through the flanges 16a and 16b it is also inserted through the slots 21 and 21a in the suspended arm. Each cap 19 is preferably made of steel or other strong material that will not yield when it engages the pin 17 for a purpose to be hereafter explained.

The bottom of each cap 19 rests on a bearing 22, that is closely fitted between the flanges 16a and 16b and that is held in place by a bolt 23.

The bearing 22 is preferably made from a high impact plastic material, such as high density Polyethylene, having good lubricity, but other materials having the desired qualities of strength and lubricity could be used, and the arm 18 is passed upwardly through a hole provided therefor in the bearing. As so arranged, the am 18 is held in vertical alignment by the bearing 22 and the cap 19, which supports the arm through pin 20, rests on and rotates on the upper surface of the bearing.

Bearings 24 and 25, which may be identical in all respects to bearing 22, and which fit tightly within the channel member 16, further assist in maintaining the vertical alignment of arm 18. Bearing 24 is mounted immediately beneath bearing 22 and is held in place by a bolt 26. This bearing, additionally serves as a back up member to take the weight of the arm and any load thereon, should the bearing 22 fail for any reason and should the cap 19 on the end of the arm fall away from pin 17. In such a situation, a person sitting on the seat 12 would then feel only a slight drop and yet would know that repairs were necessary.

Bearing 25 is spaced below bearing 24 and is held in place by a bolt 27. As has been noted, the bearing 25, also serves to hold the arm 18 in vertical alignment. In addition, bearing 25, like bearing 24 helps to prevent a complete fall of the arm in the event of structural failure of the support structure above. Thus, even in the unlikely event both bearings 22 and 24 should fail or if the pin should fail, the arm will drop only until the stud 28, which projects from the arm 18 between the bearings 24 and 25, engages the top of bearing 25. With such a short drop it is unlikely that a person sitting on the seat 12 could be injured.

The stud 28, which may for example, be a steel pin inserted into a blind hole provided therefore in the upwardly extending portion of arm 18 also serves as an anchor for the lower end of a spring 29 that is specially wound around the arm 18 and that is anchored at its upper end by a similar stud 30. The spring is hooked around the studs such that it cannot travel up or down on the arm and the spring hooks are enlarged so that studs 31 and 32, fixed to and projecting from the inside of a cover plate 33, will almost contact the arm 18 between and adjacent to the studs 28 and 30, respectively. The studs 31 and 32 thus block movement of the hooks of the spring past them, and provide means for anchoring of the spring ends, through the cover plate to the channel member 16.

While the support structure shown can be used to support a single suspension arm, it also is possible to support two such arms, as is shown in the drawings. In this case, a pair of holes are provided through the bearings 22, 24 and 25 and each arm is provided with a cap 19, having slots 21 and 21a and with a pin 20 to fasten a cap to the top of each of the substantially parallel upwardly extending portions 18a of the arms 18. The pin 17 is then passed through the slots 21 and 21a of each cap 19.

In operation, rotation of one of the arms, such as the one shown at the right in FIG. 2, in a counterclockwise direction, will move the stud 28 and the end of the spring hooked thereon away from stud 31. However, the other. end of the spring is held against rotation by stud 32 and the rotation thus winds the spring and increases the spring return force. When the suspension arm is released, the spring will move it back to its starting porition, as shown. Should the arm be rotated in the opposite direction, i.e. clockwise, the stud 30 will move the end of the spring 29 that is hooked thereon away from stud 32, but at the same time stud 31 will prevent movement of the end of the spring hooked thereon. Again the spring will wind around the arm and a spring return force will develop that will swing the arm 18 back to its starting position, as shown.

The slots 21 and 21a in cap 19 provide resilient limits to the extent that the suspension arm can be rotated in either direction. When the arm has reached the point at which it is desired that rotation of the seat towards the table be restricted, the end of the shorter slot 21 will hit pin 17 near its center. This will tend to stop such rotation before the seat back engages the edge of the table top. If, however, a great moment force is applied to the chair the pin 17, which is somewhat resilient, will elastically yield to allow continued movement of the arm until the longer slot 21a engages pin 17 near its supported end which then offers an even greater limiting force, further tending to prevent the seat back from engaging the edge of the table. When the moment force is removed,

the pin 17 will spring back to its straight condition and the seat back will be moved to a position away from the edge of the table. Similarly, collision of adjacent seats or people sitting on the seats, as they swing outwardly away from the table, is normally prevented by the other ends of slots 21 and 21a sequentially engaging pins 17. As with rotation towards the table, such engagement of the ends of the slots with the pins 17 will normally stop further rotation away from the table, but if forced, the pin will resiliently yield to some extent before breaking. A user recognizing the resistance developed would not normally continue to force the rotation such that the pin would break.

The amount of free swing of the suspension arm 18 is determined by the elongate lengths of the slots 21 and 21a cut into the sidewall of cap 19. Likewise, the length of swing before the first and second stages restricting rotation are effective is determined by the relative lengths of slots 21 and 21a. These slot lengths can be varied, as desired. The force with which the suspension arm will be returned to its starting position can be varied depending upon the spring used.

The cover plate 33 can be secured to channel member 16 in various ways, but it is presently preferred that the bolts 23, 26 and 27, be made long enough to extend through respective holes 34, 35 and 36 provided therefor through the plate.

The bolts 23, 26 and 27, may be through bolts extending fully through the web of channel 16, their respective bearings, and the cover plate before receiving nuts 37, they may be stud bolts welded to and projecting from the inside of the web of channel 16, or they may be a combination of such through bolts and stud bolts.

With the present structure, the bearings are inexpensive to construct, give maximum support, operate efficiently and are easily assembled into the support construction. The springs 29 return the suspension arms to a pre-set centering or starting position and the swinging movement is snubbed so that the seat backs will normally not engage the edge of the table, with resultant damage to either or both the table or the seat back and so that adjacent seats will not normally swing outwardly such that they will collide.

In FIGS. 4-7, there is shown another centering arrangement that can be used in place of the spring 29, and studs 28, 30, 31 and 32.

In this embodiment, the seat suspension arm, shown at 40, has an upwardly extending portion that extends upwardly through an upper single plastic bearing 41 that fits within channel 42 and held in place by a bolt 43. A cap 44, corresponding to the cap 19 previously described fits on the top of arm 40 and is held in place, resting on top of bearing 41, by a roll pin 44a. While only a single bearing 41 is shown, it should be obvious that two could be used, as disclosed in connection with the previous embodiment. Similarly, while it is not shown, it should be apparent that a pin corresponding to the pin 17 of the previous embodiment could be provided, passing through the flanges of channel 42 and slots, not shown, but provided therefor in the cap 44 of each arm 40 used.

A bearing washer 45 surrounds arm 40 and fits against the bottom of bearing 41. An expansion spring 46 telescopes around am 40 beneath the washer 45 and acts against another bearing washer 47 on top of a cam member 48.

Cam member 48 fits around arm 40, has a fiat top surface on which washer 47 rests and a pair of identical curved cam surfaces 480 and 48b extending upwardly from a low point 480 at one side of the cam member to a dwell 48d at the opposite side thereof.

Another rolled pin 49 serves as a cam follower and projects from arm 40 and normally rests in the dwell 48d as the cam member 48 is forced downwardly against the pin 49 by spring 46. Rotation of arm 40 in either direction will move pin 49 out of dwell 48d and along one or the other of the cam surfaces 48a or 48b. In either case, this moves the cam member up and compresses spring 46. When the force tending to rotate the arm is removed the spring expands causing the cam follower to move back into the dwell and thereby rotating arm back to its centered position. Rotation of the cam member 48 with the cam is prevented by sliding engagement of the flat surface 48e at the rear of the cam 48 with the web 42a of the channel 42 and/or the sliding engagement of one of the flat surfaces 48f with a side flange 42b of the channel 42.

As shown in FIG. 4, a pair of arms 40 can be used, in the same manner as the arms 18, previously described.

In FIG. 8, there is shown still another embodiment of the invention. In this embodiment, as in that of FIG. 4, a single upper bearing 50 is shown secured between the flanges 51a of a downwardly extending channel member 51 by a bolt 52 that extends through the web 51b of the channel member and the bearing and a nut 52a. Obviously, a plurality of bearings could be used instead of the single upper bearing if desired.

As shown, a pair of suspension arms 53 and 54 have their upper ends extending upwardly through the bearing 50 and a roll pin 55 is inserted through each upper end and beyond each side thereof to rest on a washer 56 above the bearing. Thus as each arm turns, the roll pin 55 thereof turns, using the washer 56 as a bearing surface or the washer turns with the arm and pin, using the upper end of the bearing as a bearing surface. The roll pins 55 also keep the arms 53 and 54 from slipping down through the bearing.

The arms 53 and 54 also extend downwardly through a lower bearing 57 that is similarly held between the flanges 510 by a bolt 58 extending through the web 51b and the bearing and nut 58a. I

A cam-return mechanism, shown generally at 60, is provided between the upper bearing and the lower bearing for each arm. Each cam-return mechanism includes -a cam member 61, telescoped around a supporting arm and fixed to the arm to be rotational the rewith, by a pin 62. The upper surface of each cam member is diagonally angled with respect to theaxis of the arm from a high point 61a to a low point 61b.

A cam follower 63 also telescopes around the arm and, because of the engagement of some of its flat outer surfaces 63a, 63b and 63c, with the channel member 51, it cannot rotate with the arm. An expansion spring 64 acts between a washer 65 on the bottom of bearing 50 and a washer 66 on the top of cam follower 63 to bias the cam follower towards the cam member 61.

The cam follower has a cam surface extending diagonally with respect to the arm axis, from a high point 630' to a low point 63e, and conforming essentially to the diagonal surface on cam member 61.

In operation, the springs 64 tend to force the cam followers 63 down. This causes the arms to tend to rotate until the upper surface of the cam members 61 and the lower surface of the cam follower are in mating relationship and the spring 64 has been extended the maximum amount possible. The arms can be rotated in either direction, in which event the cam follower will slide upwardly within channel member 51. However, as soon as the rotational force applied, as by a person sitting on chairs (not shown) at the outer end of the arms, is removed, the springs and cams will tend to rotate the arms back to a starting position.

The cam members and cam followers are preferably made of a suitable high impact plastic material having good lubricity, such as that used for the bearings 22, 50 and 57. The cam followers can be conveniently made by merely diagonally slic ing the bearings 50 or 57.

When a pair of upper bearings such as are shown in FIG. 2 at 22 and 24 are not used, it may be desirable to weld an L- shaped bracket 65, FIG. 12, to the channel 51. Bolt 52 then passes through a hole 65a in the upwardly extending leg of the bracket, and the arms 53 and 54 extend downwardly through holes 6511 and 65c, respectively in the horizontally extending leg. The bracket is welded along the edges of the horizontal leg to the flanges 51a of the channel and will support the arms even if the bearing 50 should fail.

Although a preferred form of our invention has been herein disclosed, it is to be understood that the present disclosure is by way of example and that variations are possible without departing from the subject matter coming within the scope of the following claims, which subject matter we regard as our invention.

We claim:

1. A table and suspended chair unit comprising a table top;

means for supporting said table top above the ground;

suspension means extending downwardly below said table top at a location adjacent an outer edge of the table top;

means supporting said suspension means beneath said table top, said suspension means including at least one rigidly mounted plastic bearing;

at least one suspension arm having a horizontally extending portion and an upwardly extending portion journaled through each said plastic bearing, whereby said bearing maintains said upwardly extending portion in an upright attitude;

a seat journaled about a vertical axis on the horizontally extending portion of each suspension arm for rotation thereabove; and

support means secured to the upper end of each said arm,

whereby said arm is journaled in the bearing and said support means turns on said bearing.

2. A table and suspended chair unit as in claim 1, further including yieldable means cooperating with the support means for limiting rotation of the suspension arm whereby a back on the seat is normally restrained against engagement with the edge of the table top.

3. A table and suspended chair unit as in claim 2, wherein the suspension means further includes a downwardly extending channel member and the yieldable means comprises a slightly resilient pin extending across the channel member and through at least one slot formed in a sidewall of the cap means.

4. A table and suspended chair unit as in claim 2, wherein a plurality of plastic bearings are closely fitted within and secured to the channel member and the upwardly extending portion of the suspension arm is journaled through each of said bearings.

5. A table and suspended chair unit as in claim 4, wherein the plurality of plastic bearings include a first bearing beneath the support means; and

a second bearing spaced from the first bearing.

6. A table and suspended chair unit as in claim 5,'wherein the plurality of bearings further includes a third bearing directly beneath the first bearing and spaced from the second bearing.

7. A table and suspended chair unit as in claim 1, further including means for biasing the suspension arm to a starting position regardless of the direction of rotation of the arm.

8. A table and suspended chair unit as in claim 7, wherein the means for swinging the suspension arm to a starting position includes a spring spirally wound around the suspension arm between the first and second bearings and terminating in opposed hooks,

means fixed to the suspension arm for preventing unwinding movement of each of said spring ends and for selectively moving one of said spring ends upon rotation of the arm in each direction, and

means fixed to the channel member for preventing unwinding movement of said spring ends whereby the spring end not moved by rotation of the arm in one direction is held against movement.

9. A table and suspended chair unit as in claim 8, wherein the means fixed to the channel member for preventing unwinding movement of the spring ends comprises a cover plate adapted to fit on the channel member bolt to secure the cover plate to the channel member, and

studs extending from the cover plate into positions blocking the hooks on the ends of the spring.

10. A table and suspended chair unit as in claim 7, wherein the means for swinging the suspension arm to a starting position includes a spring means;

a cam member having a cam track with a dwell therein; and

a cam follower member, said spring and said members being arranged such that said spring means acts on one of said members to constantly bias it against the other and such that one of said members is fixed to and is rotatable with the arm.

1 l. A table and suspended chair unit as in claim 10, wherein the spring means comprises a spring surrounding the arm and having one end acting on the bottom of an upper bearing;

the cam member surrounds the arm and has a flat upper surface against which the other end of the spring acts, and a pair of cam tracks extending upwardly from a low point to a dwell on a lower surface; and

the cam follower comprises a pin projecting from the arm and adapted to move with the arm and to fit into the dwell in the cam track ofthe cam member.

12. A table and suspended chair unit as in claim 7, wherein the means for swinging the suspension arm to a starting position includes spring means;

a cam member;

a cam follower member, said cam member and said cam follower member having substantially matching diagonal faces in face to constantly face relationship and being arranged such that the spring means acts on one of said members to bias it towards the other and such that one of the said members is fixed to and is rotatable with the arm.

13. A table and suspended chair unit as in claim 1, wherein a pair of suspension arms, are provided, the upwardly extending portions thereof extending substantially parallel to each other and being spaced apart.

l4. Centering apparatus for a rotatable seat suspension arm having an upwardly extending portion and a horizontally extending portion and that is supported by a rigid support structure comprising a coil spring wound around the upwardly extending portion and having opposed hooks formed in the opposite ends thereof;

means fixed to the upwardly extending portion of the suspension arm for preventing unwinding movement of each of said spring ends and for selectively moving the opposite ends of the spring when the arm is rotated in opposite directions; and

means fixed to the rigid support structure for preventing unwinding movement of said spring ends whereby the spring end not moved by rotation of the arm is held against movement.

15. Centering apparatus for a rotatable seat suspension arm having an upwardly extending portion and a horizontally extending portion and that is supported by a rigid support structure comprising spring means;

a cam member having a cam track with a dwell therein; and

a cam follower member, said spring means and said members being arranged such that said spring means acts against one of said members to constantly bias it against the other and such that one of said members is fixed to and is rotatable with the arm.

16. Centering apparatus for a rotatable seat suspension arm having rm upwardly extending portion and a horizontally extending portion and that is supported by a rigid support structure comprising spring means;

a cam member;

a cam follower member, said cam member and said cam follower member having substantially matching diagonal faces in face to face relationship and being arranged such that the spring means acts on one of said members to constantly bias it towards the other and such that one of the said members is fixsd t2 ar d rotatsble with the arm. 

1. A table and suspended chair unit comprising a table top; means for supporting said table top above the ground; suspension means extending downwardly below said table top at a location adjacent an outer edge of the table top; means supporting said suspension means beneath said table top, said suspension means including at least one rigidly mounted plastic bearing; at least one suspension arm having a horizontally extending portion and an upwardly extending portion journaled through each said plastic bearing, whereby said bearing maintains said upwardly extending portion in an upright attitude; a seat journaled about a vertical axis on the horizontally extending portion of each suspension arm for rotation thereabove; and support means secured to the upper end of each said arm, whereby said arm is journaled in the bearing and said support means turns on said bearing.
 2. A table and suspended chair unit as in claim 1, further including yieldable means cooperating with the support means for limiting rotation of the suspension arm whereby a back on the seat is normally restrained against engagement with the edge of the table top.
 3. A table and suspended chair unit as in claim 2, wherein the suspension means further includes a downwardly extending channel member and the yieldable means comprises a slightly resilient pin extending across the channel member and through at least one slot formed in a sidewall of the cap means.
 4. A table and suspended chair unit as in claim 2, wherein a plurality of plastic bearings are closely fitted within and secured to the channel member and the upwardly extending portion of the suspension arm is journaled through each of said bearings.
 5. A table and suspended chair unit as in claim 4, wherein the plurality of plastic bearings include a first bearing beneath the support means; and a second bearing spaced from the first bearing.
 6. A table and suspended chair unit as in claim 5, wherein the plurality of bearings further includes a third bearing directly beneath the first bearing and spaced from the second bearing.
 7. A table and suspended chair unit as in claiM 1, further including means for biasing the suspension arm to a starting position regardless of the direction of rotation of the arm.
 8. A table and suspended chair unit as in claim 7, wherein the means for swinging the suspension arm to a starting position includes a spring spirally wound around the suspension arm between the first and second bearings and terminating in opposed hooks, means fixed to the suspension arm for preventing unwinding movement of each of said spring ends and for selectively moving one of said spring ends upon rotation of the arm in each direction, and means fixed to the channel member for preventing unwinding movement of said spring ends whereby the spring end not moved by rotation of the arm in one direction is held against movement.
 9. A table and suspended chair unit as in claim 8, wherein the means fixed to the channel member for preventing unwinding movement of the spring ends comprises a cover plate adapted to fit on the channel member bolt to secure the cover plate to the channel member, and studs extending from the cover plate into positions blocking the hooks on the ends of the spring.
 10. A table and suspended chair unit as in claim 7, wherein the means for swinging the suspension arm to a starting position includes a spring means; a cam member having a cam track with a dwell therein; and a cam follower member, said spring and said members being arranged such that said spring means acts on one of said members to constantly bias it against the other and such that one of said members is fixed to and is rotatable with the arm.
 11. A table and suspended chair unit as in claim 10, wherein the spring means comprises a spring surrounding the arm and having one end acting on the bottom of an upper bearing; the cam member surrounds the arm and has a flat upper surface against which the other end of the spring acts, and a pair of cam tracks extending upwardly from a low point to a dwell on a lower surface; and the cam follower comprises a pin projecting from the arm and adapted to move with the arm and to fit into the dwell in the cam track of the cam member.
 12. A table and suspended chair unit as in claim 7, wherein the means for swinging the suspension arm to a starting position includes spring means; a cam member; a cam follower member, said cam member and said cam follower member having substantially matching diagonal faces in face to constantly face relationship and being arranged such that the spring means acts on one of said members to bias it towards the other and such that one of the said members is fixed to and is rotatable with the arm.
 13. A table and suspended chair unit as in claim 1, wherein a pair of suspension arms, are provided, the upwardly extending portions thereof extending substantially parallel to each other and being spaced apart.
 14. Centering apparatus for a rotatable seat suspension arm having an upwardly extending portion and a horizontally extending portion and that is supported by a rigid support structure comprising a coil spring wound around the upwardly extending portion and having opposed hooks formed in the opposite ends thereof; means fixed to the upwardly extending portion of the suspension arm for preventing unwinding movement of each of said spring ends and for selectively moving the opposite ends of the spring when the arm is rotated in opposite directions; and means fixed to the rigid support structure for preventing unwinding movement of said spring ends whereby the spring end not moved by rotation of the arm is held against movement.
 15. Centering apparatus for a rotatable seat suspension arm having an upwardly extending portion and a horizontally extending portion and that is supported by a rigid support structure comprising spring means; a cam member having a cam track with a dwell therein; and a cam follower member, said spring means and said members being arrAnged such that said spring means acts against one of said members to constantly bias it against the other and such that one of said members is fixed to and is rotatable with the arm.
 16. Centering apparatus for a rotatable seat suspension arm having an upwardly extending portion and a horizontally extending portion and that is supported by a rigid support structure comprising spring means; a cam member; a cam follower member, said cam member and said cam follower member having substantially matching diagonal faces in face to face relationship and being arranged such that the spring means acts on one of said members to constantly bias it towards the other and such that one of the said members is fixed to and rotatable with the arm. 